Electrical fuse



2 Sheets-Sheet 1 T. N m

Sept. 1

G M, GIRD Q ELECTRICAL FUSE Filed Dec f M ATTORNEYS. 4

Se t. 19, 1933. G. M. smowoom ELECTRICAL FUSE Filed Dec. 23, 1950 2 Sheets-Sheet 2 1 INVENTOR.

GordonMGMdwood wfiiwzxwd @40 9 ATTORNEYS.

Patented Septo 19, 1933 signer to Pacific Electric Manniactwng Corporation, San Francisco, Callil, a corporation of @alifiornia Application er Serial Non Eibdfil-(i 9 Claims.

This invention relates generally to electrical fuses which are employed for protecting electrical circuits. In the particular form disclosed herein the invention is of particular value when 5 used with high tension electrical distribution lines. in electrical fuses which have been used in the past to protect high tension distribution lines, I considerable difficulty has been experienced in securing rapid positive breaking of the circuit under all overload conditions. While such fuses have generally been effective under heavy over loads sumcient to burn the fuse link with explosive violence, they have not operated properly under slight overload conditions. Thus under slight overloads, fuses such as have been employed in the past frequently break down and form a leal age path for the high tension current. It is not uncommon under such conditions for fuses to catch fire, thus creating a fire hazard as well as failing to properly interrupt the circuit.

It is an object of the present invention to devise an electrical fuse which will function to secure quick and positive interruption of an electrical circuit under slight overload conditions, as well as under heavy overloads.

it is a further object of the invention to devise an electrical iuse which can be readily refilled for further use.

Further objects of the invention will from the following description in when the pre i'erred embodiment of the invention has been set forth in detail in conjunction with the accoin panying drawings. it is to be understood that the appended claims are to be accorded a range or equivalents consistent with the state oi the prior art.

Referring to the drawings:

Figure l is ,a side elevational v ew cross section illustrating a fuse incorporating principles oi the present invention.

Fig. 2 is a side elevational view, partly in cross section, illustrating a refill for the fuse of 1.

Fig. 3 is a cross-sectional detail taken along the line 3- -3 of Fig. 1.

Fig. 4 is a side elevational view lustrating suitable apparatus with which the se can be employed, to positively disconnect the fuse from its associated electrical circuit in case of an over-= load.

invention can be outlined as com prising a suitable mounting, such as a tube of L1 sulating material, which serves to enclose a fuse link. lln addition to the fuse link explosive charges or capsules are placed within the mounting and are arranged in a novel manner so as be autouatically ignited in case of an overload. Explosi of these capsules or charges serve to positively and quickly separate the ends of the conductor leads to which the fuse link is connected. and in case the fuse is mounted as shown in Fig. the entire fuse is disconnected automatically from its associated electrical circuit.

Thus referring to Fig. l of the drawings, the fuse shown therein consists of a tube 10, which is preferably made of an insulating material such as a p nolic condensate product. This tube shoul ave sulficient mechanical strength to adequatdy withstand the explosion pressures to which is subjected. Terminal contact inern bers ll are mounted upon the ends of tube 10 for making convenient electrical connection with contacts of an associated electrical circuit.

To provide a suitable mounting for contact mernbe s ll, ferrules 12 are shown affixed to the ends of tube 10, and contact members 11 have a thr aded connection 13 with these ferrules. For a purpose to be presently explained, contact being alined with and of substan e s diameter as the bore of tube so d witin tube 10 there is a refill assembly is s? in detail in Fig.

o features of the present i v ahle fuses not adapted to b er use, the use of a refill has ce advantages is considered a e assembly as shown in me i? preferably made of ins ia-ll, which when the refill asseinb er tuoe 1o. Extending into each or here is an electrical conductor lead l8,

of con actor leads 18 are connected to a suitable fuse lil 19. The use of fuse links of this char as actor is well known in the-art and their proper-- r nd the materials employed for the so oe be described in detail. it is sufiicient out that this link will fuse a predeter current value. Conductor leads 1:; errlot ten 1 closures 2i, which are fitted into the ends are i7, and which are made of some suitab c erial such as cor that the assembly of Fig. 2 can i e si into tube 10 thru one or" the contact Hil ll, to assume the normal op rating positior ovu- Fig. 1. As suitable means .or form elec" ical connection between leads e contact members 11, I have shown the .se leads coiled within the end portions 116' lid 22 of metal ferrules 12. These coiled le nortions, which have been indicated at 23, c then be expanded to make good electrical contact with the adjacent metal walls of ferrule portions 22, by means of the split expansible discs It is frequently desirable to seal the tube against en trance of moisture, and for this purpose there is shown a sealing disc 26, made of suitable mate rial such as lead, and which is clamped between contact members 11 and their associated ferrules i2. Gaskets 2'? can be inserted between the discs 26 and the adjacent surfaces of contact l= The entire space within tube 1'? is pi e. packed with. a suitable filler 25 of divided insulating material, such as crushed marble.

if the fuse as described above were employed for protecting an electrical circuit, without the provision of additional means such as will be presently explained, under slight overload conditions the fuse link 19 would not blow with explosive violence, but would tend to permit an arc to form between the inner ends of conductor leads 18. The heat of this are might also break down the insulation of tube 10, to form a direct leakage path between the contact members 11. in order to provide means to prevent such action under slight overload conditions, i provide a plurality of charges or capsules 28 or" explosive material, such as gunpowder, which are located within tubes 10 and 17 but remote from the fuse link 19. The preferred location for these charges or capsules is to have at least one charge adjacent each end of tubes 10 and 17. Furthermore the charges can either be positioned beside leads 18, or surrounding these leads as shown Fig. l. In order to automatically ignite the charges 28, I provide a resistance element in the form of a resistance wire 29, this wire being extended thru and in contact with the explosive material of charges 28, and having its ends connected to the leads 1% so as to be in shunt with the fuse link 19. I also preferably enclose that portion of wire 29 extending between the charges 28, with a tube or sheath 31 of insulating material which loosely fits over the wire. A suitable sheath or tube of this character is commonly known as insulating spaghetti.

in operating the fuse described above, assulning that an electrical circuit is connected to the contact members 11, in the event of a slight overload sufficient to melt fuse link 19, a relatively heavy current is bypassed thru resistance wire 29, so that this wire is heated sufficiently to ignite the explosion charges 28. In the event that wire 29 fuses within the tube or sheath 31, jets of in candescent material are ejected from the ends of this tube to ignite charges 28. The explosion caused by igniting these charges immediately blows out the closures 21 thru openings 14 in contact members 11, and these closures carry with them the lead conductors 18. Thus any arcing tending to occur between inner ends of leads 1% is immediately broken when the leads are jerked apart. In all observed instances it has been found that both the explosive charges have been ignited to blow out both the end closures 21. However in the event that only. one charge is ignited, the filler 25 will withstand the pressure of this explosion so that the closure 21 adjacent this charge will be expelled to withdraw its asso= ciated lead lit.

The apparatus shown in Fig. t is particularly adapted for use with the fuse described above, and makes possible automatic cutout or the fuse when the fuse blows. This apparatus consists of a suitable bracket 32 adapted to be clamped to a member 33 of a supporting structure, and serving in turn as a support for a pair of insulators 34 and 35. An arm 3'? is mounted upon and extends from insulator 35, and is provided at its outer end with a bifurcated portion 38. Bifurcated portion 38 is formed to provide a journal as for a pivot pin 41. Member 42 is carried by pivot pin 41, and secured to this member 42 there is a clamp 43 adapted to be detachably secured to one end of the fuse 44. iromthe other insulator 34, there is an arm 46 having an outer bifurcated portion 47. When in normal position the upper end of fuse 44 extends between the branches of bifurcated portion 47. Immediately above portion 4'? there is a latch 48, which is pivotally connected to arm 46 by means of pivot pin 49. The lower face of latch 4% is provided with a pocket or recess 51 which receives the upper end of contact member 11 of the fuse, when the latch is in normal position. A spring pressed contact 52 is carried between the branches of bifurcated portion 47, so as to normally engage and make good electrical contact with the upper contact member 11 of the fuse. This contact member is shown connected to a bus conductor 53, by means of jumper 54. The lower contact member 11 of the fuse is likewise aclapted to make electrical contact with a spring pressed contact 56, carried by arm 37. This contact 56 is connected to bus conductor 57 by means of flexible jumper 58. Normally contact 52 urges the upper end of fuse 44 outwardly, but the fuse is retained in operating position by latch 48. In case of an overload which will cause an explosion within the fuse as has been previously described, the force of the explosion. blowing outwardly thru the upper contact member 11, lifts latch 48, and thus permits the fuse to swing downwardly in the position shown in dotted lines in this figure. Thus in the event of an overload the fuse is positively and automatically out out from its associated electrical circuit.

I claim:

1. In an electrical fuse, a tubular member, conductor leads extending into the ends of said member, a iuse link connecting the inner ends of said leads, a filler of divided insulating material disposed within said member, means for connecting said leads and serving as closures for the endsof said member, and means for quickly withdrawing said leads from the tube in the event of an overload, said means comprising a plurality of charges of explosive material disposed within said member, a charge being located adjacent each closure, and means for simultaneously igniting said charges.

2. In an electrical fuse, a tubular member, conductor leads extending into the ends of said member, a fuse link connecting the inner ends of said leads, a filler of divided insulating material disposed within said member, means connected to said leads and serving as closures for i the ends of said member, and means for quickly withdrawing the leads from said tubular mem- Mounted upon and extending ear/gee? material packed within said member, and means for quickly withdrawing said leads from said tubular member in the event of an overload, said means including a charge of explosive material disposed within said tubular member remote from said fuse link.

4. In an electrical fuse, a tubular member, conductor leads extending into said member from the ends thereof, a fuse link connecting the inner ends of said leads, a filler of divided insulating material packed within said member, and means for quickly withdrawing said leads from said member in the event of an overload, said means including a plurality of charges of explosive material disposed within said member adjacent both ends thereof and remote from said fuse link, and electrical means for automatically igniting said charges in the event of an overload.

'5. In an electrical fuse, an outer tube, conductor leads extending into said tube from the ends thereof, closure members for the ends of said tube connected to saidleads, a fuse link connecting the inner ends of said leads, a filler of divided insulating material packed within the tube about said link and the adjacent portions of said leads, a plurality of charges of explosive material'disposed within the tube remote from said link, a charge being located adjacent each end of the tube, a resistance conductor in contact with said charges and connected in shunt with said link, and a second tube, disposed about that portion of the resistance conductor extending between said charges, said last mentioned tube serving to direct the heat'from said resistance conductor toward said explosive charges.

6. In an electrical fuse apparatus, a fuse tube, contact members mounted upon the ends of said tube, a fuse link disposed within the tube and connected to said contact members, explosive charges located in the end portions of said tube, means for effecting automatic ignition of said charges in the event of an overload, means for supporting said tube with its contacts connected with an electrical circuit, and means responsive to explosion of said charges for automatically disconnecting said contact members from said circuit.

7. In a fuse, a tube, contact members mounted upon the ends of said tubes, and a fuse refill assembly slidably insertable within said tube thru one end thereof, said assembly comprising a liner tube insertable within said first tube, conductor leads extending into said liner tube, a fuse link connecting the inner ends of said conductor, explosible charges disposed within the ends of the liner tube, a resistance element connected in shunt with said link and in contact with said charges, and a filler of divided insulating material packed within said liner tube.

.8. In an electrical fuse, a tubular member, a conductor lead extending into one end of said member, a fuse link disposed within said member and having one end thereof connected to the inner end of said lead, means for making electrical connection to theother end of said fuse link, and means for quickly withdrawing said lead from said tubular member in the event of an overload, said means including a charge of explosive material disposed within said tubular member remote from said fuse link, and a resist ance conductor connected in shunt with the fuse link for igniting said explosive material.

9. in an electrical fuse, a tubular member, a conductor lead extending into said member, a fuse link having one end thereof connected to the inner end of said lead, said link b'eing dis-. posed within said tubular member, means for making electrical connection with the other end of said fuse link, and means for quickly withdrawing said lead from said tubular member in the event of an overload, said means including a charge of explosive material disposed within said tubular member remote from the fuse link, a resistance conductor connected in shunt to the link and having one end thereof terminating adjacent said charge, and an insulating sheath surrounding said resistance conductor and likewise having one end thereof terminating adjacent said charge.

GORDON M. GIRDWOOD. 

